Adriatic sturgeon (Acipenser naccarii) were maintained on a commercial diet enriched either in long chain polyunsaturated fatty acids of the omega3 series (omega3 LCPUFA) or in saturated fatty acids (SFA). The effects of dietary fatty acid composition on spontaneous locomotor activity in normoxia and hypoxia (O2 tension = 10.5 ± 0.8 kPa), and on oxygen consumption (MO2) in normoxia, in hypoxia (O2 tension = 6.6 ± 0.8 kPa) and during recovery were then investigated. The effects of adding supplementary vitamin E to the fat-enriched diets were also studied.Dietary fatty acid composition had effects on spontaneous locomotor activity and MO2 in normoxia. Activity levels were higher in all sturgeon fed extra dietary fats (without vitamin E), when compared with control animals, but fish fed omega3 LCPUFA had a significantly lower MO2 than those fed SFA, with intermediate MO2 in controls. In hypoxia, sturgeon omega3 LCPUFA did not alter activity or MO2 whereas those fed SFA reduced both and controls reduced MO2. During recovery, both animals fed SFA and controls had a higher MO2 than sturgeon fed omega3 LCPUFA. The data indicate that fish fed omega3 LCPUFA are more tolerant of hypoxia than controls or those fed SFA, as they did not reduce either activity or MO2, and consumed less O2 during recovery.Vitamin E supplements modified the effects elicited by dietary fats. All sturgeon fed vitamin E had low activity levels in normoxia and hypoxia. Sturgeon fed vitamin E with omega3 LCPUFA had a higher MO2 in normoxia than those fed omega3 LCPUFA alone; reduced MO2 in hypoxia, and during recovery increased MO2 to a rate higher than that of animals fed omega3 LCPUFA alone. In normoxia, sturgeon fed vitamin E with SFA had a similar MO2 to those fed SFA alone but did not change MO2 in hypoxia or during recovery. Thus, the effects of vitamin E were dependent on fat composition of the diet. Vitamin E with omega3 LCPUFA removed the beneficial effects on MO2 and responses to hypoxia obtained with omega3 LCPUFA alone, but vitamin E with SFA allowed sturgeon to maintain aerobic metabolism in hypoxia, a more effective response than that observed in fish fed SFA alone.